Is underlayment required under slate, tile, or thatch roofs?
Slate, tile, and thatch materials are not completely waterproof on their own and allow moisture to pass through joints and gaps. Underlayment serves as the actual primary waterproof barrier beneath these outer coverings, while the outer material functions mainly as UV protection.
What the numbers show
Counted from the threads quoted below. How we count
- The most recent one is from October 2026.
- This comes up 43.7× more often in r/Roofing than across the site as a whole.
What people tried
Every workaround mentioned in the threads below. We haven’t tested any of them — and nobody here is claiming they worked.
Found another way around this?
Share your steps and trade-offs so fellow engineers don't have to reinvent the wheel. No account required.
- 1installing felt or underlayment anyway for extra security against wind-driven leaksDid this help you?
- 2relying purely on tight fitting slate without underlayment in certain regionsDid this help you?
- 3Consulting a contractor for an on-site assessmentDid this help you?
- 4Planning to shingle over the existing material before inspecting it closelyDid this help you?
- 5Posting on forums to ask experienced roofers for advice before proceedingDid this help you?
- 6Using the heavier material anyway because it acts as an overkill upgradeDid this help you?
In their words
Unedited, grouped by where they were said, most upvoted first within each place, each linked to the thread it came from.
“I’m installing new shingles on my shed roof and was told to use an underlayment. I have the shingles and starter shingles but I think I have the wrong underlayment. I thought the underlayment was more like roofing paper and this is very think. Could use some advice? Thanks”source ↗
“It was always my understanding during my entire career spanning over 40 years, that the slate is UV protection. The waterproofing was the underlayment. Same for tile and thatch roofs.”source ↗
“How wouldn't some water get in through those.”source ↗
“Does this need to be shingled over or am I fine to leave it as is? I live in the midwest so I get rain and wind throughout the year and heavy snow in winter.”source ↗
“Im so confused... is this face nailed cap sheet? that is not right. you do not put nails in that product and caulk over them.”source ↗
“What kind of underlayment should I use? Can you give me a type?”source ↗
“I'm confused because I'm reading things that say I need to put down a 6mil vapor barrier and a 2-3mm foam pad. But then we had a contractor come look at it, and he said today's laminate flooring has the vapor barrier and pad included. Which is it?”source ↗
Where this came up
People with this problem also raised
- 3What are these stains and damage on my attic roof sheathing?
- 2Do I need a waterproof membrane under tile or a toilet flange?
- 4Do I need underlayment for luxury vinyl plank flooring?
- 3Are my skylights deck mounted or curb mounted?
- 2Do I need a vapor barrier over rigid foam in a basement?
- 8Do I need a waterproof membrane under tile on a concrete floor?